Modify the auto-placement setting of a Dedicated host. When
auto-placement is enabled, AWS will place instances that you launch
with a tenancy of host , but without targeting a specific
host ID, onto any available Dedicated host in your account which has
auto-placement enabled. When auto-placement is disabled, you need to
provide a host ID if you want the instance to launch onto a specific
host. If no host ID is provided, the instance will be launched onto a
suitable host which has auto-placement enabled.